The present invention relates to a device and method for measuring a particle diffusion coefficient, and particularly to a device and method for measuring a diffusion coefficient of particles of suspensions, in which colloids, nano-particles, bio-macromolecules, inorganic particles or the like are dispersed, when the particles are transported through micropores of a hollow-fiber.
To date, many studies on diffusion of particles through the confined spaces of micropores have been conducted. In most of these known studies dealing with flat type membranes, an electrolyte introduced into a diffusion cell is stirred for promoting the diffusion and then a measurement is performed to detect a change of particle concentration, in order to measure the diffusion coefficient.
The followings are publications related to the particle diffusion through the confined micropores.
In the journal of xe2x80x9cChemical Engineering Sciencexe2x80x9d, Volume 33, Issue 11, Dermot M. Malone and John L. Anderson propose a diffusion cell by which the hindered diffusion behavior of latex particles with diameter of 91 nm in a track-etched flat type membrane having well-defined cylindrical micropores of a preset size, can be observed. They also disclose results of the hindered diffusion coefficient according to a change in the ionic concentration (i.e. ionic strength) of potassium chloride electrolyte solution with respect to various micropores having a different size.
Imtiaz A. Kathawalla and John L. Anderson disclose the measurements of hindered diffusion coefficient for the linear flexible chain of polystyrene with dilute concentration (molecular weight: 1.6-9.3xc3x97105 Daltons) through the micropores of track-etched flat type membrane made of mica, in the journal of xe2x80x9cIndustry and Engineering Chemistry, Researchxe2x80x9d, Volume 27, Issue 5. This reference proposes a diffusion cell for the flat type membrane, which has a simple configuration and is more efficient in delivering the solutions thereinto, compared to existing units.
Jeenok T. Kim and John L. Anderson describe a study on both the hindered diffusion phenomenon and the hydrodynamic thickness developed near a wall surface of micropores in a situation where the macromolecular dextrans with different molecular weights are transported through the micropores adsorbed with polystyrene sulfonate in the xe2x80x9cJournal of Membrane Sciencexe2x80x9d, Volume 163, pages 163-182. They used a track-etched flat type membrane made of mica and detected a minute change of the concentration caused by diffusion by employing a fluorescent probe method in which the optical fibers are applied.
In the journal xe2x80x9cLangmuirxe2x80x9d, Volume 5, Issue 4, Keith A. Johnson et al. disclose results of a hindered diffusion coefficient of the micelle measured where the micelle was diffused through the straight cylindrical micropores of flat type membrane made of polycarbonate. They exemplified a case in which the radius of colloidal particles is ten times larger than that of the micropores and the ionic strength of electrolyte solution is low, so as to show that the long-range interaction between colloidal particles and the wall surface of the micropores has a considerable influence on the particle diffusion.
In the xe2x80x9cJournal of Colloid and Interface Sciencexe2x80x9d, Volume 153, Issue 2, Nelson P. Lin and William M. Deen disclose a study on measurement of a hindered diffusion coefficient of potassium polystyrene sulfonate, which is a polyelectrolyte, with respect to the micropores of flat type membrane. This reference shows that the experimental measurements fairly coincide with the theoretical prediction.
In the xe2x80x9cAmerican Institute of Chemical Engineers Journalxe2x80x9d, Volume 46, Issue 6, Jiahui Shao and Ruth E. Baltus measure the hindered diffusion coefficients of both the dextrans with molecular weights of 1.6-6.2xc3x97105 Daltons and the polyethylene glycol with a molecular weight of about 11xc3x97105 Daltons, through the micropores with sizes of 0.03, 0.05, and 0.1 xcexcm in a track-etched flat type membrane made of polycarbonate. When the Stokes-Einstein equation is applied with the measurements, the respective theoretical radii were 3.6-5.3 nm for dextran and 3.0 nm for polyethylene glycol. From a comparison between the measurements and the model prediction, they show that, besides the steric exclusion and the electrostatic repulsion, the van der Waals attraction also affects on the hindered diffusion coefficient.
In the xe2x80x9cAmerican Institute of Chemical Engineers Journalxe2x80x9d, Volume 46, Issue 7, Jiahui Shao and Ruth E. Baltus measure a hindered diffusion coefficient of the same solute particles as used in the above described reference, taking concentrations of about 20, 42, and 60 mg/mL through the same membrane as used in the above described reference. They compared the experimental values of the diffusion coefficient depending on an increase of the particle concentration with the model prediction, and analyzed the hindered diffusion behavior in view of the related interaction potential.
All of the above described studies and citations are related to the measurements of hindered diffusion coefficient through the micropores of flat type membranes, however, they cannot really be applied to the micropores of hollow-fiber having a different geometrical configuration from the flat type membrane.
Therefore, there has been a need for developments of a method and device for measuring a diffusion coefficient of particles through the micropores of hollow-fiber.
It is, therefore, an object of the present invention to provide a device and method for measuring particle diffusion coefficient by flowing both a particle suspension and a electrolyte solution in a xe2x80x9ccon-currentxe2x80x9d mode, where the particle suspension flows through an inner space (i.e., tube-side) of a hollow-fiber, while the electrolyte solution flows through an outer space (i.e., shell-side) of the hollow-fiber, thereby measuring the diffusion coefficient through the micropores of the hollow-fiber in a short time with small amount of the feed solution.
The object and other objects, which will become apparent to those skilled in the art, are accomplished with a measuring device of particle diffusion coefficient provided with a hollow-fiber including micropores on its surface. The hollow-fiber provides a passage for a particle suspension to transport through. The device is also provided with a fluid passage formed outside the hollow-fiber to communicate with the hollow-fiber via the micropores. The fluid passage provides a passage for an electrolyte solution to transport through in such a manner that the electrolyte solution is delivered to flow in a same direction as that of the particle suspension and is discharged from the fluid passage. The device detects a concentration change of the particles in the electrolyte solution discharged out of the fluid passage over a time change and calculates a particle diffusion coefficient by using the concentration change of the particles over the time change.
In accordance with one aspect of the present invention, a method of particle diffusion coefficient measurement is provided. The method comprises the steps of (a) flowing a first fluid having particles into the inside of a hollow-fiber and flowing a second fluid into the outside of a hollow-fiber in a same direction as that of the first fluid, the fluid passage communicating with the inside of the hollow-fiber; (b) discharging the second fluid; (c) detecting a change in the particle concentration in the second fluid being discharged out of the fluid passage over the time change; and (d) calculating a diffusion coefficient by using the concentration change of the particles over the time change.
In accordance with another aspect of the present invention, the method described above further comprises the steps of calculating a hindered diffusion coefficient by using the concentration change of the particles over the time change and the particle diffusion coefficient.